The invention relates to improvement in bags, and more particularly to a plastic bag chain wherein the series of bags are interconnected for handling, filling and sealing and the interconnection may be broken to separate bags from the chain.
In reclosable bags of the type referred to, pressure interlocking reopenable and reclosable rib and groove or zipper elements are formed along the top on confronting faces adjacent the bag top. A completed plastic bag of this type has flanges above the rib and groove elements to open the bag when it is used. However, these flanges in their original form were joined and later slit apart during the manufacturing process. The front and back walls are joined to each other along side seams, and the bottom edge is normally continuous to close the bag, or the bottom edges may be joined to form the seam. Reclosable plastic bags of this nature are disclosed, for example, in U.S. Pat. Nos. 3,198,228, 3,291,177, 3,338,284 and 3,340,116.
Bags of this type have been formed in chains, and in a machine adapted to receive such a chain, the rib and groove elements are separated for filling the bags, and then rejoined, after which the individual bags are torn from the chain for use. However, if any particle of material being filled or foreign element inadvertently gets between the rib and groove element, it will prevent satisfactory closure. Further, to make the bag tamper-proof evident requires an additional sealing and perforation operation that adds cost to the machine as well as complexity.
To overcome this problem, the bag chain can be run upside down, with the profiles at the bottom and with their respective flanges left united, while the bottom of the bag is slit and run at the top. However, such an arrangement cannot run through a chain bag type filling machine, since the film has to be properly guided and supported or it will collapse. Therefore, it is necessary to provide, near the upturned bottom edge of the bag chain, one or more guiding ridges. These ridges allow the bag chain to be handled in the same way as a regular bag chain where the profiles are used as a support and guide means.
It is accordingly an object of the present invention to provide an improved bag chain structure wherein reclosable bags are used, and the rib and groove elements are maintained locked throughout the filling and handling operation so as to avoid the possibility of improper rejoining of the rib and groove element, and to provide above the elements a tamper-proof evident means.
A still further object of the invention is to provide an improved bag structure wherein the bags may be filled through the bottom and wherein the bags can be handled by automatic machinery with accurate alignment of the bottom edges of the bag and the bags do not collapse or wrinkle or fold during their handling and during their being drawn through the machine.
A still further object of the invention is to provide an improved bag chain wherein the adjacent bags are joined by frangible links which are associated with the bag structure in such a manner that the bags, even when formed of very flexible thin, lightweight material, will retain their position in an automatic filling machine and can be handled in a relatively high speed filling and closing operation.
A feature of the invention is to provide a chain of bags which are inverted wherein the rib and groove elements are suspended downwardly and the bag is carried through a machine with the bottom edges of the bag faced upwardly and separated. Strengthening and supporting ribs are carried on the surface of the bag adjacent the bottom edges which reinforce the bag, hold the bottom edges straight and tend to prevent the bag from folding or wrinkling. For utilizing the maximum effect of the ribs, the bag is supported by the ribs on upwardly facing machine shoulders which engage beneath the ribs. Frangible interconnecting links are formed between the bags, and in one preferred form, the link is in alignment with the rib being formed of plastic from the rib by applying a heating element in the area of the rib to reduce the thickness of the plastic and reduce the width of the frangible link to a desired width which will break with a predetermined pull. In another form, plural links are used with one link being formed in alignment with the rib and another link being formed in alignment with the rib and groove elements.
Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which: